Ringing code detector



Feb. 2, 1960 e. RICHARDS RINGING CODE DETECTOR Filed Dec. 14, 1956 sSheets-Sheet 2 lNl NTOR GLENN L. RICHARDS BY A T TORNEY Feb. 2, 1960 G.L. RICHARDS RINGING coma: DETECTOR Filed Dec. 14, 1956 s Sheets-Sheet 3INPUT 2 RING CODE APPLIED TO LINE ll' l rI r1 mm START NG ANODE FIFIIINGPOTENTI! L k f 0F V-I I 0F V-l aRlNc STARTING A\|ODE FIRING POTENT ALPAD W OF v-2 WW\ OF v-z I STARTING ANODE FIRING POTENTIAL OF v-a OF V-3533% v OUTPUT APPLIED TO RINGER I Z 3 4 0 2 3 14 9 2 3 1 ,INPuT ILONGRING APPLIED TO LINE S-IIARHNG ANODE I' IRIIG POTENTIAL OF v-I OF V-l I2 RING PAD /ST'ARTING ANODE FIRING POTENTIAL or v-2 OF v-2 STARTINGANODE FIRING POTENTIAL OF v-s 0F v-s l RING PAD IIIIII OUTPUT AP= III:|2 ]'0 RINGER I I I j/ 2 3 4 2 a {4 a a 4 lNI/ENTOR GLENN L. RICHARDSA T TOPNE V 2,923,776 RINGING CODE DETECTOR Glenn L. Richards, Arnes,Iowa, assignor to General Dynamics Corporation, Rochester, N.Y., acorporation Delaware Application December 14, 1956, Serial No. 628,394 2Claims. (Cl. 179-47) f" 2,923,776 [Cg Patented Feb. 2, 1960 5 lymaintain an established condition which will allow lhi ringing currentto enter the ringing circuit at the begin ning of the second ring of thetwo ring code. Therefor only the second ring of the two ring code willoperat the station ringer and the effect there will be exactly th sameas at those stations where the one ring code is effec tive, that is, astandard ringing pattern is provided s that each station will be rung ina standard manner 2 though it were on a single party line.

The slow relaxation circuit embodied in this circu This inventionrelates to telecommunication systems to pass the two ring code consistsof a gas trigger tub and particularly to code ringing arrangements forparty line telephone systems.

The object of the invention is to provide substation means which willrespond to code ringing potentials aphaving a starting anode connectedin a circuit which wi initially respond to excitation by presenting apotenti: above that required to fire the tube but where the pi tentialof this starting anode will shortly fall below suc plied to a substationline and render efiective only the point and where this loweredpotential will be maintain:

particular code to which the particular substation is arranged torespond.

As a specific example of code ringing arrangements, attention isdirected tothc copending application of for a substantial period evenafter the excitation has bet removed so that whenexcited by a secondring, them! which is quenched between rings cannot be triggered secondtime. This immediately operated tube is. er

George Elliott, Serial Number 432,755, filed May 27, ployed to place aload on a voltage divider circuit lea 1954. Here is provided a meanswhereby a plurality of substations are connected to a line andarrangements are made to call these stations by one ring and two ringcodes. It therefore appears thatthc substations will be grouped in pairsand both substations of each pair will respond fir t ring of a two ringcode comes to the same ringing current, it being left to the subscribersto mentally differentiate between the one ring and two ring codes. It isdesirable, however, to sound the substation bell only when the partythereat is wanted. The object of the present invention is to provide acircuit means at each substation which will pass only that code to whichthe particular substation is intended to respond.

The invention resides in a pair of electronic circuits, a first of whichwill respond to a two ring code and will exclude a one ring code and asecond of which will admit a one ring code and will exclude a two ringcode. This arrangement is possible due to the fact that standard andconventional arrangements are such that the two rings of a two ring codeare each much shorter than the one ring of a one ring code. It will benoted, in the Elliott arrangement, that the total ringing time of eachcode is the same, it being continuous in the case of the one long ringcode and being divided and spaced apart in two equal intervals in thecase of the two short ring code.

In accordance with the means provided to pass a long ring but exclude atwo ring code, an electronic circuit having a timing means for reachinga given stage of operation in a period just over the length of one ringof a two ring code is provided and controlled by a fast actingrelaxation circuit whereby the operation of this timing means will haveto be started from the beginning at the beginning of the second ring ofthe two ring code with the result that a two ring code cannot pass intothe ringing circuit. However, if a one long ring is received, the saidtiming circuit will operate and will pass the ringing current into theringing circuit for the last half of the code. The particular station,arranged to respond to the one long ring code will therefore be rungalthough the actual length of the ring will not be as long as that 65provided by the ringing arrangements.

In accordance with the means provided to pass a two ring code but toexclude a one long ring code, means is provided to immediately respondto the beginning of a ring either a short ring of a two ring code or along ring of a one ring code and to establish an excluding condi- -'tionto exclude the ringing current from the bell circuit ing to the startinganode of the main ringing curre passing tube so that this last tube isprevented from o crating during the first ring of a two ring code orduri' the whole of a one long ring code. However, when t to an end, this10 will be relaxed as the first of these tubes ceases to cc duct. Thepotential of thestarting anode of this fi tube, however, is maintainedat a value below the critii value of this tube so that when ringing.current is ag:

transmittedinto the circuit this first tube is prevent from firing andsince it can no longer impose a load thesaid voltage divider circuit,the potential of the st: ing anode of the second tube will rise aboveits criti value and this last tube will thereupon conduct ring currentto the substation ringer.

A feature of the invention is the use of two types substation padcircuits, one for use at a substation ranged to be signalled by a singlelong ring code and other to be signalled by a two short ring code whichonly respond to such codes and will translate such co to a uniformsingle ring code. Each pad will respi to a particular code and each willexclude all other cc but will produce a standard output, the same at alltions.' While the one ring signal thus produced is about the same lengthas one ring of a two ring cod is still adequate for substation signalingand it has virtue of being the same at all stations and being e1 tive atonly that station intended to respond to a pa ular code. Thus eachsubscriber will only be ca 5 when actually wanted.

Another feature of the invention is a circuit m requiring a doubleapplication of current thereto for dering means, to pass such current toa use circuit, e tive, in which a first application of current is empltto block said means and to establish a condition w will persist over aperiod constituting a silent period code and which established conditionwill, on a set application of current, render said blocking mean:effective.

Another feature of the invention is the use of a tr tube for loading thecircuit of a relay means to prt the operation thereof and the use of atrigger pote circuit for said trigger tube having a time constant thatits initial high potential surge is reduced to a 1 below a criticalvalue and maintained at such depr value over a period of no excitationfor a predetern length of time. This trigger tube has a starting .a

:ircuit which will respond to an initial energization to )roduce apotential above a critical value but which will [uickly fall below suchcritical value and then block any vttempt to raise it above suchcritical value for a preletermined time whereby such trigger tuberendered nononducting cannot be triggered into operation again with- 1such predetermined time.

Another feature of the invention is an electronic ciruit acting withinits first two steps as a scale of two evice whereby it requires asuccession of at least two nergizing intervals to reach a desired state.By such ieansa circuit may be constructed and arranged to repond to atwo ring code on .a telephone line and to :ject any one ring code.

Other features will appear hereinafter.

The drawings consist of three sheets having six figres, as follows:

Fig. 1 is a schematic circuit diagram of a two ring ad for excluding allone ring codes and for. passing a nging signal triggered by a two ringcode to the subation where it is located, the pad being shown con- :ctedto one of the line wires and arranged to respond ringing currentsuperimposed on a positively biased lrrent;

Fig. 2 is the same circuit but arranged to respond to Jging currentsuperimposed on a negatively biased curnt; Fig. 3 is a schematic circuitdiagram of a one ring .d for excluding all two ring codes and forpassing a lging signal triggered by a one long ring code to the bstationwhere it is located, the pad being shown concted to one of the linewires and arranged to respond ringing current superimposed on apositively biased rrent; Fig. 4 is the same circuit as that of Fig. 3arranged respond to ringing current superimposed on a negaely biasedcurrent; Fig. 5 is a set of graphs plotted against time to show a tworing code input, the response of the two ring 1, the response of the onering pad and the output ging signals at the substation provided with thetwo g pad; and Fig. 6 is a Similar set of graphs plotted against time toPW the one long ring code input, the response of the ring pad, theresponse of the one long ring pad I the output ringing signals at thesubstation provided h the one long ring pad. .ooking at Fig. 1 it willbe noted that to the line which may be either the tip or ring of atelephone at the substation, there is connected a two ring I usefulunder given circumstances for connecting a ;er 2 through a triggeredtube V-2 to ground so that ringing current flowing over the line willoperate the ger to attract the attention of the subscriber thereat. 5circuit of Fig. 1 is arranged to respond to ringing rent superimposedonly on a positively biased current, the anode of the tube V-2 must bepositively biased. he ringing current is superimposed on a negatively:ed current, then the pad must be connected as m in Fig. 2 where theanode of the tube V-2 will Jositive with respect to its cathode. fterthe tube V1 is fired and as the condensers C-2 C-3 attain their charge,the potential at the junction esistances R3 and R4 is lowered to a pointconsiderbelow the potential required for firing the tube V I, this tubehaving been fired nevertheless remains in mducting state and thiscondition will continue as as ringing current is transmitted overline 1. ie two ring pad of Figs. 1 and 2 is constructed and iged toenable the ringer 2 only in response to a ring code and to prevent theenabling of the ringer :sponse to a one long ring code. The outstandingre of the operation of this circuit is that a first er tube V-l isimmediately fired before the con densers C-2 and 0-3 can have beencharged and by the conduction of current from its main anode to itscathode will depress the potential at the junction of resistances R-5and R-6 and likewise depress the potential at the junction of theresistances R-6 and R-7 below the firing potential of the tube V-3. Aslong as the ringing current is supplied to this circuit, then, the tubeV-3 will be prevented from firing and thus the circuit will not respondto a one long ring code. However, at the end of any ring which causedthe firing of the tube V-l, the charge on the condensers C-2 and C-3will begin to dissipate. If now the silent interval is short as betweenthe two rings of a two ring code, these two condensers do not becomefully discharged and the following application of ringing current willnot produce a surge to provide a firing potential to the starting anodeof the tube V-l and hence this tube fails to fire and consequently thefull potential of the network is applied across the voltage dividerconsisting of the resistances R-S, R-6 and R-7 and consequently thepotential at the starting anode of the tube V-2 rises sufficiently forthis tube to fire. Since the continuation of the ringing current merelydrives the condensers 0-2 and C-3 to full charge, the tube V]. will notfire and the tube V-2 will remain active.

In somewhat more detail the circuit of Fig. 1 operates in this manner.The diode 3 isolates the circuit from the talking conductor 1, and theV-2 tube while inactive performs the same function during the talkingperiod. When ringing current appears on the line 1, this being of higherpotential, it passes through the diode 3, the R-1 resistance and thecondenser C1. The variable resistance R-l is used to compensate for theeffect of line loss and is notreset after its. initial adjustment on aparticular installation. The two condensers C-1 and C-2 and the tworectifier diodes d and 5 constitute a voltage doubling direct currentpower supply. The NEE neon diode is used as a voltage regulator and theR2 resistance limits the peak currents through the voltage regulator.

The C-2 condenser charges up in relatively short time after the ringingcurrent appears on the line 1. The C-3 condenser couples this large andrapid voltage change to the starting anode of V-ll and then as it startscharging brings the potential of the starting anode down toward theproportion of the supply voltage determined by the voltage dividercircuit R3 and R-4. As a result of the initial voltage surge on thestarting anode, the starting anode to cathode gap breaks down and thetube V4 then fires through the resistance R-5. With the main anode ofthe tube V-l conducting, the potential at the junction of theresistances R-6 and R-7 is too low to trigger the tube V-2.

The above described action takes place every time that ringing currentis transmitted over the line whether the bias is positive or negative.If the detector is attached for positive bias, as shown in Fig. l, andnegative bias is connected to the line, 1-2 will not conduct no matterwhat ringing code is applied. Likewise, a detector connected fornegative bias as shown in Fig. 2 cannot conduct ringing current withpositive bias applied because of the characteristics of the gas relaytube V2.

The detector of Figs. 1 and 2 is meant to allow the ringer in thesubscribers telephone set to ring When the code is a two short ringcode. The operation is depicted in Fig. 5 Where the two short ringingintervals are shown as covering the periods t to Z and t to 1. Thegraphs in the bracket marked 2 ring pad show the potentials at thestarting anodes of the tubes V-l and V- 2. The condenser C-i charges upvery shortly after time t and since the tube V1 immediately fires thepotential on the starting anode of tube V2 is held below the valuenecessary for the firing of this tube. At time 1 the condenser C-2begins to discharge through the high resistance bridge R-3 and R-4 andthe condenser -3 likewise begins to discharge through R-3. However, thetime constant is such that the potential at the starting anode of thetube V-l is held at a value below the firing point of this tube wherebywhen ringing current is again applied to the line at time t;.,, V-l isprevented from firing and there now being no load on the resistance R-S,the potential at the starting anode of V-2 rises beyond the criticalvalue. Therefore during the interval between time and t the tube V-Zwill conduct ringing current through the ringer 2.

When the code is the one long ring, the action is depicted in Fig. 6.Here the tube V-1 is immediately fired and since there is a load on theresistance R- the potential of the starting anode of V-2 remainsconstantly below the critical value from time t to time t, and the tubeV-2 does not fire.

The long time constant of this circuit is shown by the slow decay of thepotential of the starting anode of V-2 between times t and t and betweentimes t and the next t in Fig. 5 and between times t and the next 1 inFig. 6. It will be understood that these graphs have been idealized tobring out clearly the operation of the circuits of the presentinvention.

In both Figs. 5 and 6, certain areas have been fille in during the timethat ringing current is applied to the line and during which the tubeV-2 (in Figs. 1 and 2) and tube V-3 (in Figs. 3 and 4) are made toconduct. The lowermost graph in both Figs. 5 and 6, marked output,represent the application of ringing current to the ringer 2. It will benoted that the 2 ring pad (of Figs. 1 and 2) and the one long ring pad(of Figs. 3 and 4) both produce an output consisting of one short ringbetween times t and t and since these are produced at difierentsubstations on the same party line it will simulate the operation of asingle party line and no subscriber will be annoyed by having to listento codes used to summon other parties on the line.

The operation of the one ring pad of Figs. 3 and 4 is somewhat diiferentsince there is no intermediate tube to fire immediately to hold thepotential of the fired tube down. The time constant of this circuitdiffers as shown in Figs. 5 and 6, in that the build up of the potentialon the starting anode of the tube V-3 is slow and will not reach thecritical value within the limits of one of the short rings. Therefore asshown in Fig. 5 in the graph marked 1 ring pad, the potential of thestarting anode of V-3 rises slowly during the first ring of a two ringcode and reaches a critical value just beyond the time and then dropsquickly so that at time t the action starts over from the beginning.Thus the 1 ring pad (of Figs. 3 and 4) will pass no ringing current on atwo ring code. However, when a long ring is applied to the line asdepicted in Fig. 6, the potential of the starting anode of V-3 willreach the critical value shortly after time i so that ringing currentwill be applied to the ringer 2 for the remainder of the one long ring.

By this means each substation of a party line may be provided with anelectronic circuit powered entirely by current transmitted over the lineand will convert the coded ringing current to a different code tosimulate the operation of a single party line.

The value of the various components marked on the drawings and thecommercial designations used are by way of example and are used merelyto give a clear understanding of the spirit of the invention.

What is claimed is:

1. In a telephone system, a subscriber line having a plurality ofsubstations thereon and each substation having a ringer, means forselectively signaling said substations consisting of means for applyingcoded ringing current thereto including codes of two short rings andcodes of one long ring, an electronic circuit at each said stationintended to be signaled by a two short ring code, said circuit havingtwo electronic tubes and being responsive to ringing current transmittedthereto over said subscriber line for rendering a final one of saidtubes conducting in response to a second application of said ringingcurrent thereto closely following a first application of said ringingcurrent thereto and for preventing the enablement of said final tube inresponse to a single application of said ringing current thereto, saidcircuit including a first tube having means to block the enablement ofsaid final tube, a triggering circuit for said first tube consisting ofa voltage divider, a mid tap therefor constituting a triggeringconductor and a condenser bridged about one half said voltage dividerand acting when uncharged to communicate the potential applied to saidvoltage divider to said triggering conductor and when charged tocommunicate the potential of said mid tap to said triggering conductor,and a circuit for said ringer controlled by said final tube.

2.In a telephone system, a subscriber line having a plurality ofsubstations thereon and each said substation having a ringer, means forselectively signaling said sub stations consisting of means for applyingcoded ringing current thereto including codes of two short rings andcodes of one long ring, an electronic circuit at each said substationintended to be signaled by a two short ring code, said circuit havingtwo electronic tubes and being responsive to ringing current transmittedthereto over said line for rendering a final one of said tubesconducting in response to a second application of said ringing currentthereto, closely following a first application of said ringing currentthereto and for preventing the en ablement of said final tube inresponse to a single application of said ringing current thereto, saidcircuit including a rectifying means for deriving a direct current fromsaid ringing current, a voltage divider circuit having a high potentialportion and a low potential portion connected to said direct currentsource, a mid tap from said voltage divider, a condenser bridged acrossthe high potential portion of said voltage divider circuit, a first tubefor controlling said final tube and a triggering circuit for said firsttube controlled by said mid tap connection, and a circuit for saidringer controlled by said final tube.

References Cited in the file of this patent UNITED STATES PATENTS2,411,525 Deakin Nov. 26, 1946 2,490,054 Hatton Dec. 6, 1949 2,753,403Caracciolo July 3, 1956 2,788,394 Barrow et al. Apr. 9, 1957 2,790,851Berch Apr. 30, 1957 2,798,950 Edrich July 9, 1957 2,800,584 Blake July23, 1957

